Disk drives are an important data storage technology, which include several crucial components. Disk drive read-write heads directly communicate with a disk surface containing the data storage medium over a track on the disk surface. This invention involves improving the ability to position at least one read-write head over the track on the disk surface.
FIG. 1A illustrates a typical prior art high capacity disk drive 10 including actuator arm 30 with voice coil 32, actuator axis 40, suspension or head arms 50–58 with slider/head unit 60 placed among the disks 12.
FIG. 1B illustrates a typical prior art high capacity disk drive 10 with actuator 20 including actuator arm 30 with voice coil 32, actuator axis 40, head arms 50–56 and slider/head units 60–66 with all but one disk 12 removed as well as including spindle motor 80.
Since the 1980's, high capacity disk drives 10 have used voice coil actuators 20–66 to position their read-write heads over specific tracks. The heads are mounted on head sliders 60–66, which float a small distance off the disk drive surface when in operation. Often there is one head per head slider for a given disk drive surface. There are usually multiple heads in a single disk drive, but for economic reasons, usually only one voice coil actuator.
Voice coil actuators are further composed of a fixed magnet actuator 20 interacting with a time varying electromagnetic field induced by voice coil 32 to provide a lever action via actuator axis 40. The lever action acts to move head arms 50–56 positioning head slider units 60–66 over specific tracks with speed and accuracy. Actuator arms 30 are often considered to include voice coil 32, actuator axis 40, head arms 50–56 and head sliders 60–66. Note that actuator arms 30 may have as few as a single head arm 50. Note also that a single head arm 52 may connect with two head sliders 62 and 64.
Today, read-write head positioning errors are a significant point of failure and performance degradation. These positioning errors are caused in part by disk fluttering. Some fluttering problems for disks can be attributed to instabilities in the motor turning the disk, which are being addressed by the motor manufacturers.
The disk drive industry faces some significant challenges. As either recording densities or spindle speed increases, both head positioning accuracy and head-flying stability must increase. Note that competitiveness in the disk drive industry requires both requires both increased recording density and increased spindle speeds. Note that head-flying is the motion of the read-write head over the disk surface, which flies a short distance off that surface.
In order to achieve an even higher track density essential for meeting the higher recording density requirements, the allowable position error of the heads relative to registered data tracks is required to be less than 0.05 μm for the next few years.
New ways to improve head positioning and stabilize head-flying are needed to meet these challenges, as well as improve the reliability of existing disk drives.